If you can download a Movie here and it says that it is under the Creative Commons license: Public Domain
the entire work is in the Public Domain.
So you`r free to use the Musik Score from that Movie for what ever you like ...
Dangerous advice above. Many PD films contain music covered by publishing rights, and some contain "needle drop" music that is still being licensed by various libraries. Using such music in your own productions could possibly open you to liability.